U.S. Pat. No. 6,382,560 to Ow discloses a high speed vertical take-off and land (HSVTOL) aircraft. The aircraft includes a disk-shaped fuselage with a rotatable fan assembly having a nozzle ring driven by hot jet gases and fan air from jet engines. High efficiency air bearings serve to support the rotatable fan assembly on the fuselage in the vertical direction and rollers around the perimeter provide horizontal support and stability. The present invention relates to an improvement of this basic design by incorporating an active system for sensing vibration and balancing the fan assembly as it is rotated.